Method for measuring the degree of uniformity of compositions



2,936,377 1 Patented May 1-o,, 19 so METHOD FOR MEASURING THE DEGREE OF UNIFORMITY OF COMPOSITIONS James F. Black, Roselle, and Eric 0. Forster, Hillside,

N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware N Drawing. Application November 29, 1954 Serial No. 471,884

3 Claims. (Cl. 250-106) This invention relates to a method for measuring the degree of uniformity of compositions and more particularly concerns the use of the radioactive isotope iodine 132 as a means for measuring the degree of uniformity of compositions, particularly oleagino-us compositions such as lubricating oils and greases wherein at least two components are blended or mixed together to prepare the finished composition.

In'general, it is highly desirable to market products having a uniform composition. Many products, such as gasolines, heating oils, fuel oils, diesel oils, rust preventive compositions, asphalts, lubricating oils, lubricating greases, fertilizers, cements, flours, pigments, and the like are blends, mixtures, solutions, suspensions or the like of a number of separate components. Considerable effort is expended in blending, mixing, stirring, milling,

homogenizing, etc. such compositions to obtain substannecessary to produce a substantially uniform composition is time consuming and expensive. It thus would be highlydesirable to have available an eifectivemethod for measuring the efficiency of mixing, which method would be accurate, rapid, simple and inexpensive. Heretofore it is not believed that there was such a method.

It has now been found that the efficiency of mixing and the uniformity of compositions may be effectively measured by using the radioactive isotope iodine 132. Briefly, the method of the present invention comprises adding a small, but radioactively detectable, amount of iodine 132 to a composition containing at least two compohents, mixing the components of said composition containing iodine 132, and thereafter measuring the radioactivity of a portion of the mixed composition. The

"radioactivity of the mixed composition may be measured, for example, by withdrawing a small sample from the total composition and measuring the radioactivity of -this sample. -By comparing the measured radioactivity of the sample with the calculated radioactivity of a sample of an ideally mixed composition, it is thereby possible to determine the eificiency of the mixing. The difference between the measured value and the calculated value is an indication of the efficiency of the mix- "ing operation. Thus a measured value either above or below the calculated value indicates that the composition is not entirely uniform. In another method of meas- 'ur ing the radioactivity of a portion of the mixed composition, a stream of the mixed composition flowing at Fasubstantially constant rate is continuously monitored "with a "radiation 'rate counter during the mixing operation and the amount of fluctuation in the radioactivity detected by the radiation rate counter is a measure of the non-uniformity of the composition.

The compositions which may be employed in the present invention include finely divided crushed, ground or powdered solids as well as liquid compositions. The present invention is particularly effective with compositions which may be termed liquid compositions and it will be understood that the tennliquid as used herein includes normally liquid compositions as well as those semi-liquid compositions such as lubricating greases and asphalts which can be made to flow at mixing conditions. It will thus be apparent that the method of the present invention may be employed with a wide variety of compositions which are prepared by blending or mixing at least two components together to thereby form. a substantially uniform composition. The method of this invention may thus be employed in measuring the efiiciency of mixing of, for example, motor gasolines, aviation gasolines, diesel fuels, heating oils, residual fuels, asphalts, lard, lubricating oil compositions, lubricating grease compositions, asphalts, fertilizers, cements, flours, pigments and the like. The present invention is especially useful in preparing substantially uniform compositions containing at least one relatively viscous component. The method of this invention is thus especially useful for determining the uniformity of oleaginous compositions, such as lubricating oil compositions and particularly lubricating grease compositions, since such compositions are relatively viscous in nature and require considerable mixing to prepare a substantially uniform composition. i

Iodine 132 is a radioactive isotope of iodine. Since iodine 132 has a half life of only 2.33 hours, it hasa definite advantage over radioactive isotopes having long half lives. Thus iodine 132 may be added to a composition in accordance with this invention and used to determine the uniformity of the composition and thereafter, in a relatively short period of time (e.g. 12 hours the radiation from the iodine 132 will substantially disappear due to radioactive decay to form the inert gas xenon, which is volatile and non-radioactive and which does not affect the quality of the product composition being tested for uniformity. The radiation emitted by iodine 132 ,is essentially beta rays and some gamma rays andthe intensity of this radiation is such that it may be readily detected by conventional radiation detectors. Since iodine 132 is available in the. pure form without contamination with any inactive carrier, very small amounts are sufficient to permit the desired tracing operation. Iodine 132 is particularly adapted for use in petroleum products in which it is soluble without chemical reaction. However, it should be noted that aireaction by addition of iodine 132 to a component-of a composition is not objectionable since death of iodine 132 restores the status quo.

Iodine 132 is available as a by-product of uranium 235. More particularly, tellurium 132 is a radioactive fission product of uranium 235, and tellurium 132 (which has a half life of 77 hours) decays by giving off a beta particle to form iodine 132. Solid tellurium dioxide is presently available and can be readily treated to obtain a solution of iodine 132. More specifically, when a sample of fresh iodine 132 is desired, the solid tellurium dioxide may be dissolved in aqueous sodium hydroxide. The tellurium dioxide is then precipitated with acetic acid, the iodine 132 remaining in solution. The iodine 132-containing solution may then be readily separated from the tellurium dioxide precipitate by decantation. This particular treating operation can be re-performed after a period of time of about 15 hours to therebyobtain another fresh solution of iodine 132 from the tellurium dioxide.

In accordance with. the present invention, a solution of this iodine l32 is measured for its radioactivity and is then added to the composition which is to be tested for uniformity. The amount of the iodine 132 which is utilized will, of course, depend upon the size of the total batch'which is to be mixed and, of course, should be sufiicient such that the radioactivity of the mixed cornposition-may be readily detected by radiation detectors. For practical considerations, it is preferred to add enough iodine 132 such that the initial activity of the total composition containing the iodine 132 is at least about 0.1 microcuries/lb. of total composition. Preferably, the initial radioactivity of the total composition containing the iodine 132 is in the range of about 1 microcurie/lb. to 20 microcuries/lb. Higher activities may be used if desired, but are not necessary and will increase the cost of the determination for uniformity. It will be understood of course that the amount of iodine 132 employed will be dependent upon the quantity of the composition to be tested aswell as the approximate mixing time to be utilized, which time preferably is in the range of about 0.1"to 10.0 hours. Larger batches and longer mixing times each require that a greater total amount of iodine 132 be added to the composition batch.

In accordance then with the present invention, an op timum amount (based on the batch size and the approximate mixing time anticipated) of iodine 132 is added to the composition which is to be mixed or blended to thereby obtain a substantially uniform composition. The composition containing the iodine 132 is then mixed for a certain period of time (t). Then in accordance with one embodiment of this invention, a sample of the mixed composition is withdrawn from the total batch and its radioactivity is measured and this measured value is compared with a value calculated for a sample of the ideal- 1y mixed composition. The calculated value may be determined from the following equation:

t=%g t where R equals the original measured activity of the fresh iodine 132; F equals the fraction of the original iodine 132 which is active after time t; W is equal to the weight ofthe total composition being measured for uniformity; and A, equals the activity of the iodine 132 per unit weight after time vt.

- Thus if R is expressed in terms of disintegrations/sec- 0nd and W is expressed in terms of grams, A, will be expressed in terms of disintegrations/second/gram. If the measured value of the sample of the mixed composition is dilferent, that is either higher or lower, than the calculated value, this is a showing that the composition is not uniform. The amount of the difference, one way or the other, is an indication of the degree of non-uniformity. F may be readily calculated from the formula -t E5 e TI/Z where t has the same definition as described above, that is, the time elapsing from the time the sample of fresh iodine 132 is obtained by treating tellurium dioxide and is measured for its radioactivity to the time when the sample of the mixed composition is measured for its radioactivity; and T is the half life of iodine 132 which is a constant and is equal to about 2.33 hours.

Suitable radiation detectors which may be employed for measuring the radioactivity of the sample of the mixed composition include Geiger counters, proportional counters, scintillation detectors (using any of the scintillation crystals well known to the art), or ionization chambers. In the case a system of continuous monitoring is employed, a scintillation detector having a crystal which "2,936 33 a re m is surrounded by a collimating shield is preferred. The detector is oriented so that it detects activity from only a single local spot in the unit.

As has been stated heretofore, the method of this invention is especially useful in determining the degree of uniformity of oleaginous compositions such as lubricating oil compositions and lubricating grease compositions. In general, lubricating oil compositions usually comprise a major proportion of a lubricating oil base stock and minor proportions of one or more additive materials, The lubricating oil base stock may be straight mineral lubricating oils or distillates derived from parafiinic, naphthenic, asphaltic, or mixed base crude, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constituents have been carefuly removed. These mineral oils may be refined by conventional methods such as acid, alkali and/ or clay treating, solvent extraction, solvent dewaxing, and the like. Also, for special applications, various animal, vegetable or fish oils may be employed. Also, synthetic hydrocarbon oils may be employed as well as the new classes of synthetic lubricants such as esters, complex esters,halocarbon oils, esters of phosphoric acid, alkyl silicates, sulfite esters, carbonates, mercaptals, formals, polyglycol type synthetic oils and the like. If desired, mixtures of any of the above may be employed.

The lubricating oil base stocks, however they may have been produced, may vary considerably in viscosity and otherproperties, depending upon the particular use for which they are desired, but theyrusually range from about 40 to seconds Saybolt viscosity at 210 F. These lubricating oil base stocks may be compounded with one or more additive materials to prepare useful lubricating pil compositions. Such additive materials include detergents such as sulfonates, metal phenates, metal alcoholate's, metal alkyl phenol sulfides, metal organo phosphates, triophosphates, phosphosulfurized hydrocafbons, and the like, dyes, pour depressors, heat thickened fatty oils, sulfurized fatty oils, organo metallic compounds, metallic or other soaps, sludge dispersers, foam suppressing agents, anti-oxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, voltolized fats, voltolized mineral oils, and/or voltolized waxes and colloidal solids such as graphite or zinc oxide, etc., solvents, assisting agents and the like. These additive minerals are generally added to the lubricating oil and are mixed thoroughly therein by mechanically agitating the lubricating oil composition. Such agitation can be produced by recycle or double action paddles, homogenizers, or by forcing a stream of air or inert gases through the lubricating oil composition or by any other means conventionally used in such operations.- Suchlu- The soaps are prepared by saponifying high molecular weight carboxylic acids, such as those having from about 12 to 30 carbon atoms, preferably those having about 18 to 22 carbon atoms per molecule. These acids may be derived from straight or unsaturated naturally occurring or synthetic fatty materials. The fatty acids normally used in the manufacture of greases include stearic,

hydroxystearic, dihydroxystearic, polyhydroxystearic, and

.other saturated hydroxy fatty acids, arachidic, hydrogenated fish oil, tallow acids,'etc. Also unsaturated acids such as oleic, ricinoleic or similar acids may'likewise be used The soaps of these acids include those of alkali fnetals, alkaline earth metals and other grease-forming metals, such as calcium, sodium, lithium, aluminum and the like, as well as mixed base soaps such as soda-lime. The thickener may be also a complex soap-salt thickener such as a complex of a high molecular weight carboxylic acid soap with a low molecular weight carboxylic acid salt, such as calcium acetate. In addition to the lubricating oil base stock and the grease thickener, lubricating grease compositions may contain other additive materials such as dyes, foam suppressing agents, anti-oxidants, oiliness agents, rust inhibitors and the like. The preparations of such greases are well known in the art and are described in detail in Lubricating Greases: Their Manufacture and Use by Klemgard. After the lubricating grease compositions are prepared, they are generally thoroughly mixed by means of mills, homogenizers, mixers and the like. These particular finishing operations are also well known to those skilled in the art and are also described in detail in the textbook by Klemgard. Frequently the lubricating grease composition is initially formed in a grease-making kettle and is then continuously withdrawn as a stream from the greasemaking kettle and passed through a mixing device, such as a mixer, mill, homogenizer or the like, and then recycled back to the grease-making kettle until a substantially uniform grease composition is prepared.

The invention will be more fully understood by reference to the following example. It is pointed out, however, that the example is given for the purpose of illustration only and is not to be construed as limiting the scope of the present invention in any way. In this example, it is desired to determine the degree of uniformity of a lubricating grease composition having the following formulation:

Composition: Weight percent Acetic acid (glacial) 3.20 Hydrogenated castor oil 2.50 Hydrofol acids 51 12.50 Hydrated lime 4.35 Phenyl alpha naphthylamine 0.50 Mineral lubricating oil 2 76.95

Hydrogenated fish oil acids corresponding to commercial stearic acid in number of carbon atoms and in degree of ii gli i lienic type mineral oil distillate having a viscosity of 55 S.S.U. at 210 F. This lubricating grease composition is prepared by charging the hydrogenated castor oil, the Hydrofol acids and the hydrated lime and all of the mineral oil to a fireheated grease kettle equipped with a double action paddle stirrer and the mixture is heated with stirring to about 130 F. The acetic acid is then added andheating is continued with stirring until the temperature increases to about 500 F. After reaching 500 F., heating is discontinued and the grease is cooled to 200 F. while stirring, at which point the phenyl alpha naphthylamine, which is an anti-oxidant, is added to the grease composition.

Then 30 cc. of a solution of fresh iodine 132 is prepared by treating solid tellurium dioxide in the manner heretofore described. This solution of fresh iodine 132 has a measured activity (R of millicuries (mc.) which corresponds to 3.7 10 disintegrations per second. This solution of iodine 132 is then added to the lubricating grease composition described above which is contained in the grease-making kettle and which is being stirred by means of the double action paddle stirrer.

The total weight of the contents of the grease-making kettle is about 10,000 lbs. (W). The grease composition (containing iodine 132) is withdrawn from the bottom of the grease-making kettle as a stream and is passed into a Gaulin homogenizer operating at a high rate of shear (about 250,000 reciprocal seconds). The homogenized product is recycled back into the grease-making kettle. During this homogenization operation, the double action paddle stirrer in the grease kettle is continuously operated and this stirring operation and the homogenization are continued for a period of 2 hours (t). At this point three l-gram samples of the lubricating grease composition in the grease kettle are taken from different spots in the kettle and their radioactivity is measured by means of a Geiger counter. The activity of each of the three grease samples as measured by the radiation detector is about 46 disintegrations per second.

The measured values are then compared with the calculated value for the ideally mixed lubricating grease composition. 7

F, is calculated as follows:

0.693 2 e (2.33 and this value of F, is substituted in the formula to give the following result:

A 3.7 X 10 510,000x453 X 0.55=46 disintegrations/sec.

As the measured radioactivity value of each of the three grease samples corresponds to the calculated radioactivity value, this shows that the lubricating grease composition which has been homogenized is a substantially uniform composition. Had the measured radiation values been less or more than 46 disintegrations per second, this would have indicated that the lubricating grease composition was not a uniform composition. Thus, for example, had the samples given radioactivity values of 40, and 51 disintegrations per second, this would have shown that homogenization should have been continued for a greater length of time in order to obtain a substantially. uniform composition.

Another way of measuring the efi'iciency of mixing is carried out as follows: A counting rate meter such as a scintillation detector with a directionally shielded (collimated) head attached to a Technical Measurements Corporation S.G. 1-A sealer is placed at the exit of, or the inlet to, the homogenizer and the counting rate recorded as the lubricating grease composition flows by. As mixing progresses, fluctuations in the counting rate become smaller and smaller and eventually disappear when ideal mixing has been achieved. This may be readily and accurately determined since the radioactivity of iodine 132 is sufiiciently strong when used in optimum concentration to be detected with conventional radiation detectors through steel conduits having a wall thickness of, for example, Vs". This second method which has just been described is preferred since it does not require the removal of samples of the lubricating grease composition from the grease kettle nor does it require a calculation of the radim activity of a sample of an ideally mixed lubricating grease composition. In either of the two methods described above, it will be understood that the iodine 132 may be added to the grease-making kettle prior, during or after the grease-making procedure is carried out or at any time during the homogenization step. The radioactive measurement for uniformity must, of course, be carried out during the measurable radioactive life of iodine 132.

To sumarize briefly, the present invention provides the art with an accurate, rapid, simple and inexpensive method for measuring the efiiciency of mixing of at least two components to form a substantially uniform composition. The present invention is particularly useful in preparing substantially uniform liquid compositions. The term liquid composition as used herein includes both those materials which are generally considered as liquids as well as those considered as semi-liquids, such as lubricating greases for example. The method of the present invenis epi 1y seiu for measu ng, the effieiencyo g thefuniformity oi oleaginous compositions s lubricating oil compositions and particularly lubrigrease compositions, However, the present invent on may be used with equally desirable results in deterng the efiiciency of mixing of finely divided solids compositions aswell as other types of liquid compositions. The 'present invention comprises adding a small, but radioactively detectable, amount of iodine 132 to the composition, mixing the components of the composition containing iodine 1'32 fora period of time and thereafter measuring the: radioactivity of a portion of the mixed composition, it will be understood that the method of this invention may be employed to test (1) the efficiency of a particular mixing operation and/or (2) the uniformity of a particular mixed composition.

What is claimed is:

1. In a process wherein an oleaginous lubricating comp n. i formed b mixin o e a e s two o p nents, one of which is a lubricating oil having a viscosity in the range of 40 to 150' seconds Saybolt at 210 F.; the method of determining the uniformity of mixing of the components which comprisesadding iodine 132 to said composition in an amount of at least 0.1 microcurie per pound, mixing the components for a period of time not exceeding the measurable radioactive life of said iodine .312., measuring the. radioactivity occasioned. by aid iodine; '32 f a por o the wmro on s x d and hea comparing the measured activity with a standard to, deter iriine the unitormity .of said composition, the uniformityof distribution of said iodine 132.being directly related to the unformity of saidcomposition because of the solubility of said iodine 132 in said lubricating oil.

2. The process of claim 1 wherein said compositionis a lubricating grease comprising a major proportion of said lubricating oil thickened to grease consistency a grease thickener.

3. The process. of claim 1 wherein the amount of said iodine 132 added to said composition is in the range of. l to 20 microcuries. per pound of; composition.

ReferencesCited in the filtl of this patent UNITED STATES PATENTS 2,058,714 ui n e1- 21,123.16 20 2,365,553v Hill]; Dec. 19, 19.44 2,477,776 Talbot et al. Aug. 2,1949

OTHER REFERENCES Radioactive Isotopes as Tracers, by A. W. Kramer, from Power Plant Engineering, November 1947, pages, 105-108. 

1. IN A PROCESS WHEREIN AN OLEGINOUS LUBRICATING COMPOSITION IS FORMED BY MIXING TOGETHER AT LEAST TWO COMPONENTS, ONE OF WHICH IS A LUBRICATING OIL HAVILNG A VISCOSITY IN THE RANGE OF 40 TO 150 SECONDS SAYBOLT AT 210*F., THE METHOD OF DETERMINING THE UNIFORMITY OF MIXING OF THE COMPONENTS WHICH COMPRISES ADDING IODINE 132 TO SAID COMPOSITION IN A AMOUND OF AT LEAST 0.1 MICROCURIE PER POUND, MIXING THE COMPONENTS FOR A PERIOD OF TIME NOT EXCEEDING THE MEASURABLE RADIOACTIVE LIFE OF SAID IODINE 132, MEASURING THE RADIOACTIVITY OCCASIONED BY SAID IODINE 132 OF A PORTION OF THE COMPOSITION SO MIXED AND THEN COMPARING THE MEASURED ACTIVITY WITH A STANDARD TO DETERMINE THE UNIFORMITY OF SAID COMPOSITION, THE UNIFORMITY OF DISTRIBUTION OF SAID IODINE 132 BEILNG DIRECTLY RELATED TO THE UNIFORMITY OF SAID COMPOSITION BECAUSE OF THE SOLUBILITY OF SAID IODINE 132 IN SAID LUBRICATING OIL. 